Two 1941 Routers then to LAN

[CompCJtoo]

Hello.  I'm trying to configure two 1941 routers that'll connect via a shdsl connection and one of them connecting to the existing LAN.  I'd like to trunk down a few of the existing LAN vlans too for a couple of end user devices.

The problem I'm having is getting the existing LAN vlans to be up between the two 1941 routers and have inter-vlan communication.  I've attached relevant configs of both 1941 routers and a diagram too.  As it stands I'm encountering the following:

-using source vlan 972 of Rtr2 it can't ping vlan 972 on Rtr1

-from the LAN I can ping vlan 972 of Rtr 1 only

Any thoughts or suggestions greatly appreciated.  Thanks.

[Deepak Kumar]

Hi, 

This is called overlapping subnets issue. As you are using both (Rtr1 and Rtr2)are routing devices with the same subnet on VLAN 972. This is not possible without NAT. 

What is happening in your network (LAB) now:

When you are trying to ping Rtr2 VLAN IP from Rtr1 then actually Rtr1 is not sending any packet to Rtr2 because Rtr1 is thinking that he is having this subnet in his routing table that is self-connected and that IP is not available on Rtr1 network so packet dropped on network and Rtr1 assume that there is no device available with this IP.

Regards,

Deepak Kumar

[CompCJtoo]

Deepak,

Thanks for the response.  I'm a bit confused on how I'd configure NAT if I wanted to have the end user devices on Rtr2 receive an IP address via DHCP.  Would I have to create another L3 interface on Rtr1 to have both an inside and outside NAT interface.  Currently I have Gi0/0/0 trunked to the LAN for all existing VLANs.

[Deepak Kumar]

Hi, 

NAT you need to configure with new loopback interface on both routers. 

But my suggestion to go with another subnet at RTR2. 

Regards,

Deepak Kumar